Signaling format for WLANS

ABSTRACT

A method for wireless communication begins by determining whether legacy devices are within a proximal region of the wireless communication. The method continues, when at least one legacy device is within the proximal region, formatting a frame to include: a legacy preamble; a signal field; an extended preamble; at least one additional signal field; at least one service field; an inter frame gap; and a data field.

This patent application is claiming priority under 35 USC § 119 to sixco-pending patent applications: The first is entitled CONFIGURABLESPECTRAL MASK FOR USE IN A HIGH DATA THROUGHPUT WIRELESS COMMUNICATIONhaving a Ser. No. of 10/778,754, and a filing date of Feb. 13, 2004; thesecond is entitled FRAME FORMAT FOR HIGH DATA THROUGHPUT WIRELESS LOCALAREA NETWORK TRANSMISSIONS having a Ser. No. of 10/778,751, and a filingdate of Feb. 13, 2004; the third is entitled HIGH DATA THROUGHPUTWIRELESS LOCAL AREA NETWORK RECEIVER, having a Ser. No. of 10/779,245,and a filing date of Feb. 13, 2004; the fourth is entitled MULTIPLEPROTOCOL WIRELESS COMMUNICATIONS IN A WLAN, having a provisional Ser.No. of 60/544,605 and a filing date of Feb. 13, 2004, the fifth isentitled WIRELESS COMMUNICATION BETWEEN STATIONS OF DIFFERING PROTOCOLS,having a provisional Ser. No. of 60/546,622 and a filing date of Feb.20, 2004, and the sixths has the same title as the present patentapplication and has a provisional Ser. No. 60/575,921 of and aprovisional filing date of Jun. 1, 2004.

BACKGROUND OF THE INVENTION

1. Technical Field of the Invention

This invention relates generally to wireless communication systems andmore particularly to supporting multiple wireless communicationprotocols within a wireless local area network.

2. Description of Related Art

Communication systems are known to support wireless and wire linedcommunications between wireless and/or wire lined communication devices.Such communication systems range from national and/or internationalcellular telephone systems to the Internet to point-to-point in-homewireless networks. Each type of communication system is constructed, andhence operates, in accordance with one or more communication standards.For instance, wireless communication systems may operate in accordancewith one or more standards including, but not limited to, IEEE 802.11,Bluetooth, advanced mobile phone services (AMPS), digital AMPS, globalsystem for mobile communications (GSM), code division multiple access(CDMA), local multi-point distribution systems (LMDS),multi-channel-multi-point distribution systems (MMDS), and/or variationsthereof.

Depending on the type of wireless communication system, a wirelesscommunication device, such as a cellular telephone, two-way radio,personal digital assistant (PDA), personal computer (PC), laptopcomputer, home entertainment equipment, et cetera communicates directlyor indirectly with other wireless communication devices. For directcommunications (also known as point-to-point communications), theparticipating wireless communication devices tune their receivers andtransmitters to the same channel or channels (e.g., one of the pluralityof radio frequency (RF) carriers of the wireless communication system)and communicate over that channel(s). For indirect wirelesscommunications, each wireless communication device communicates directlywith an associated base station (e.g., for cellular services) and/or anassociated access point (e.g., for an in-home or in-building wirelessnetwork) via an assigned channel. To complete a communication connectionbetween the wireless communication devices, the associated base stationsand/or associated access points communicate with each other directly,via a system controller, via the public switch telephone network, viathe Internet, and/or via some other wide area network.

For each wireless communication device to participate in wirelesscommunications, it includes a built-in radio transceiver (i.e., receiverand transmitter) or is coupled to an associated radio transceiver (e.g.,a station for in-home and/or in-building wireless communicationnetworks, RF modem, etc.). As is known, the transmitter includes a datamodulation stage, one or more intermediate frequency stages, and a poweramplifier. The data modulation stage converts raw data into basebandsignals in accordance with a particular wireless communication standard.The one or more intermediate frequency stages mix the baseband signalswith one or more local oscillations to produce RF signals. The poweramplifier amplifies the RF signals prior to transmission via an antenna.

As is also known, the receiver is coupled to the antenna and includes alow noise amplifier, one or more intermediate frequency stages, afiltering stage, and a data recovery stage. The low noise amplifierreceives inbound RF signals via the antenna and amplifies then. The oneor more intermediate frequency stages mix the amplified RF signals withone or more local oscillations to convert the amplified RF signal intobaseband signals or intermediate frequency (IF) signals. The filteringstage filters the baseband signals or the IF signals to attenuateunwanted out of band signals to produce filtered signals. The datarecovery stage recovers raw data from the filtered signals in accordancewith the particular wireless communication standard.

As is further known, the standard to which a wireless communicationdevice is compliant within a wireless communication system may vary. Forinstance, as the IEEE 802.11 specification has evolved from IEEE 802.11to IEEE 802.11b to IEEE 802.11a and to IEEE 802.11g, wirelesscommunication devices that are compliant with IEEE 802.11b may exist inthe same wireless local area network (WLAN) as IEEE 802.11g compliantwireless communication devices. As another example, IEEE 802.11acompliant wireless communication devices may reside in the same WLAN asIEEE 802.11g compliant wireless communication devices. When legacydevices (i.e., those compliant with an earlier version of a standard)reside in the same WLAN as devices compliant with later versions of thestandard, a mechanism is employed to insure that legacy devices knowwhen the newer version devices are utilizing the wireless channel as toavoid a collision.

For instance, backward compatibility with legacy devices has beenenabled exclusively at either the physical (PHY) layer (in the case ofIEEE 802.11b) or the Media-Specific Access Control (MAC) layer (in thecase of 802.11g). At the PHY layer, backward compatibility is achievedby re-using the PHY preamble from a previous standard. In this instance,legacy devices will decode the preamble portion of all signals, whichprovides sufficient information for determining that the wirelesschannel is in use for a specific period of time, thereby avoidcollisions even though the legacy devices cannot fully demodulate and/ordecode the transmitted frame(s).

At the MAC layer, backward compatibility with legacy devices is enabledby forcing devices that are compliant with a newer version of thestandard to transmit special frames using modes or data rates that areemployed by legacy devices. For example, the newer devices may transmitClear to Send/Ready to Send (CTS/RTS) exchange frames and/or CTS to selfframes as are employed in IEEE 802.11g. These special frames containinformation that sets the NAV (network allocation vector) of legacydevices such that these devices know when the wireless channel is in useby newer stations.

As future standards are developed (e.g., IEEE 802.11n and others), itmay be desirable to do more than just avoid collisions between newerversion devices and legacy devices. For instance, it may be desirable toallow newer version devices to communication with older version devices.

Therefore, a need exists for a method and apparatus that enablescommunication between devices of multiple protocols within a wirelesscommunication system, including wireless local area networks.

BRIEF SUMMARY OF THE INVENTION

The signaling format for WLANs of the present invention substantiallymeets these needs and others. In one embodiment a method for wirelesscommunication begins by determining whether legacy devices are within aproximal region of the wireless communication. The method continues,when at least one legacy device is within the proximal region,formatting a frame to include: a legacy preamble; a signal field; anextended preamble; at least one additional signal field; at least oneservice field; an inter frame gap; and a data field.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 is a schematic block diagram of a wireless communication systemin accordance with the present invention;

FIG. 2 is a schematic block diagram of a wireless communication devicein accordance with the present invention;

FIG. 3 is a schematic block diagram of another wireless communicationdevice in accordance with the present invention;

FIG. 4 is a diagram of a configurable spectral mask in accordance withthe present invention;

FIG. 5 is a diagram of example spectral masks in accordance with thepresent invention;

FIG. 6 is a diagram of a wide bandwidth channel with respect to legacychannels in accordance with the present invention;

FIG. 7 is a schematic block diagram of a wide bandwidth communication inaccordance with the present invention;

FIG. 8 is a schematic block diagram of another wide bandwidthcommunication in accordance with the present invention;

FIG. 9 is a schematic block diagram of yet another wide bandwidthcommunication in accordance with the present invention;

FIG. 10 is a diagram of a backward compatible signaling format inaccordance with the present invention; and

FIG. 11 is a native signaling format in accordance with the presentinvention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 is a schematic block diagram illustrating a communication system10 that includes a plurality of base stations and/or access points 12and 16, a plurality of wireless communication devices 18-32 and anetwork hardware component 34. The wireless communication devices 18-32may be laptop host computers 18 and 26, personal digital assistant hosts20 and 30, personal computer hosts 24 and 32 and/or cellular telephonehosts 22 and 28. The details of at least some of the wirelesscommunication devices will be described in greater detail with referenceto FIG. 2.

The base stations or access points 12-16 are operably coupled to thenetwork hardware 34 via local area network connections 36, 38 and 40.The network hardware 34, which may be a router, switch, bridge, modem,system controller, et cetera provides a wide area network connection 42for the communication system 10. Each of the base stations or accesspoints 12 and 16 has an associated antenna or antenna array tocommunicate with the wireless communication devices in its regionalarea, which is generally referred to as a basic service set (BSS) 11,13. Typically, the wireless communication devices register with aparticular base station or access point 12 or 16 to receive servicesfrom the communication system 10.

Typically, base stations are used for cellular telephone systems andlike-type systems, while access points are used for in-home orin-building wireless networks. Regardless of the particular type ofcommunication system, each wireless communication device includes abuilt-in radio and/or is coupled to a radio. The radio includes a highlylinear amplifier and/or programmable multi-stage amplifier as disclosedherein to enhance performance, reduce costs, reduce size, and/or enhancebroadband applications.

Wireless communication devices 22, 23, and 24 are located in an area ofthe wireless communication system 10 where they are not affiliated withan access point. In this region, which is generally referred to as anindependent basic service set (IBSS) 15, the wireless communicationdevices communicate directly (i.e., point-to-point or point-to-multiplepoint), via an allocated channel to produce an ad-hoc network.

FIG. 2 is a schematic block diagram illustrating a wirelesscommunication device that includes the host device 18-32 and anassociated radio, or station, 60. For cellular telephone hosts, theradio 60 is a built-in component. For personal digital assistants hosts,laptop hosts, and/or personal computer hosts, the radio 60 may bebuilt-in or an externally coupled component. In this embodiment, thestation may be compliant with one of a plurality of wireless local areanetwork (WLAN) protocols including, but not limited to, IEEE 802.11n.

As illustrated, the host device 18-32 includes a processing module 50,memory 52, radio interface 54, input interface 58 and output interface56. The processing module 50 and memory 52 execute the correspondinginstructions that are typically done by the host device. For example,for a cellular telephone host device, the processing module 50 performsthe corresponding communication functions in accordance with aparticular cellular telephone standard.

The radio interface 54 allows data to be received from and sent to theradio 60. For data received from the radio 60 (e.g., inbound data), theradio interface 54 provides the data to the processing module 50 forfurther processing and/or routing to the output interface 56. The outputinterface 56 provides connectivity to an output display device such as adisplay, monitor, speakers, et cetera such that the received data may bedisplayed. The radio interface 54 also provides data from the processingmodule 50 to the radio 60. The processing module 50 may receive theoutbound data from an input device such as a keyboard, keypad,microphone, et cetera via the input interface 58 or generate the dataitself. For data received via the input interface 58, the processingmodule 50 may perform a corresponding host function on the data and/orroute it to the radio 60 via the radio interface 54.

Radio, or station, 60 includes a host interface 62, a basebandprocessing module 64, memory 66, a plurality of radio frequency (RF)transmitters 68-72, a transmit/receive (T/R) module 74, a plurality ofantennas 82-86, a plurality of RF receivers 76-80, and a localoscillation module 100. The baseband processing module 64, incombination with operational instructions stored in memory 66, executedigital receiver functions and digital transmitter functions,respectively. The digital receiver functions include, but are notlimited to, digital intermediate frequency to baseband conversion,demodulation, constellation demapping, decoding, de-interleaving, fastFourier transform, cyclic prefix removal, space and time decoding,and/or descrambling. The digital transmitter functions include, but arenot limited to, scrambling, encoding, interleaving, constellationmapping, modulation, inverse fast Fourier transform, cyclic prefixaddition, space and time encoding, and/or digital baseband to IFconversion. The baseband processing modules 64 may be implemented usingone or more processing devices. Such a processing device may be amicroprocessor, micro-controller, digital signal processor,microcomputer, central processing unit, field programmable gate array,programmable logic device, state machine, logic circuitry, analogcircuitry, digital circuitry, and/or any device that manipulates signals(analog and/or digital) based on operational instructions. The memory 66may be a single memory device or a plurality of memory devices. Such amemory device may be a read-only memory, random access memory, volatilememory, non-volatile memory, static memory, dynamic memory, flashmemory, and/or any device that stores digital information. Note thatwhen the processing module 64 implements one or more of its functionsvia a state machine, analog circuitry, digital circuitry, and/or logiccircuitry, the memory storing the corresponding operational instructionsis embedded with the circuitry comprising the state machine, analogcircuitry, digital circuitry, and/or logic circuitry.

In operation, the radio 60 receives outbound data 88 from the hostdevice via the host interface 62. The baseband processing module 64receives the outbound data 88 and, based on a mode selection signal 102,produces one or more outbound symbol streams 90. The mode selectionsignal 102 will indicate a particular mode as are illustrated in themode selection tables, which appear at the end of the detaileddiscussion. For example, the mode selection signal 102 may indicate afrequency band of 2.4 GHz, a channel bandwidth of 20 or 22 MHz and amaximum bit rate of 54 megabits-per-second. In this general category,the mode selection signal will further indicate a particular rateranging from 1 megabit-per-second to 54 megabits-per-second. Inaddition, the mode selection signal will indicate a particular type ofmodulation, which includes, but is not limited to, Barker CodeModulation, BPSK, QPSK, CCK, 16 QAM and/or 64 QAM.

The baseband processing module 64, based on the mode selection signal102 produces the one or more outbound symbol streams 90 from the outputdata 88. For example, if the mode selection signal 102 indicates that asingle transmit antenna is being utilized for the particular mode thathas been selected, the baseband processing module 64 will produce asingle outbound symbol stream 90. Alternatively, if the mode selectsignal indicates 2, 3 or 4 antennas, the baseband processing module 64will produce 2, 3 or 4 outbound symbol streams 90 corresponding to thenumber of antennas from the output data 88.

Depending on the number of outbound streams 90 produced by the basebandmodule 64, a corresponding number of the RF transmitters 68-72 will beenabled to convert the outbound symbol streams 90 into outbound RFsignals 92. The transmit/receive module 74 receives the outbound RFsignals 92 and provides each outbound RF signal to a correspondingantenna 82-86.

When the radio 60 is in the receive mode, the transmit/receive module 74receives one or more inbound RF signals via the antennas 82-86. The T/Rmodule 74 provides the inbound RF signals 94 to one or more RF receivers76-80. The RF receiver 76-80, which will be described in greater detailwith reference to FIG. 4, converts the inbound RF signals 94 into acorresponding number of inbound symbol streams 96. The number of inboundsymbol streams 96 will correspond to the particular mode in which thedata was received. The baseband processing module 60 receives theinbound symbol streams 90 and converts them into inbound data 98, whichis provided to the host device 18-32 via the host interface 62. For afurther discussion of an implementation of the radio, or station, 60refer to co-pending patent application entitled WLAN TRANSMITTER HAVINGHIGH DATA THROUGHPUT, having a provisional Ser. No. of 60/545,854, and aprovisional filing date of Feb. 19, 2004 and co-pending patentapplication entitled WLAN RECEIVER HAVING AN ITERATIVE DECODER, having aprovisional Ser. No. of 60/546,051 and a provisional filing date of Feb.19, 2004.

As one of average skill in the art will appreciate, the wirelesscommunication device of FIG. 2 may be implemented using one or moreintegrated circuits. For example, the host device may be implemented onone integrated circuit, the baseband processing module 64 and memory 66may be implemented on a second integrated circuit, and the remainingcomponents of the radio 60, less the antennas 82-86, may be implementedon a third integrated circuit. As an alternate example, the radio 60 maybe implemented on a single integrated circuit. As yet another example,the processing module 50 of the host device and the baseband processingmodule 64 may be a common processing device implemented on a singleintegrated circuit. Further, the memory 52 and memory 66 may beimplemented on a single integrated circuit and/or on the same integratedcircuit as the common processing modules of processing module 50 and thebaseband processing module 64.

FIG. 3 is a schematic block diagram illustrating a wirelesscommunication device that includes the host device 18-32 and anassociated radio 61. For cellular telephone hosts, the radio 61 is abuilt-in component. For personal digital assistants hosts, laptop hosts,and/or personal computer hosts, the radio 61 may be built-in or anexternally coupled component. The host device 18-32 operates asdiscussed above with reference to FIG. 2.

Radio 61 includes a host interface 62, baseband processing module 64, ananalog-to-digital converter 111, a filter module 109, an IF mixing downconversion stage 107, a receiver filter 101, a low noise amplifier 103,a transmitter/receiver switch 73, a local oscillation module 74, memory66, a digital transmitter processing module 76, a digital-to-analogconverter 78, a filter module 79, an IF mixing up conversion stage 81, apower amplifier 83, a transmitter filter module 85, and an antenna 86.The antenna 86 may be a single antenna that is shared by the transmitand receive paths as regulated by the Tx/Rx switch 73, or may includeseparate antennas for the transmit path and receive path. The antennaimplementation will depend on the particular standard to which thewireless communication device is compliant. The baseband processingmodule 64 functions as described above and performs one or more of thefunctions illustrated in FIGS. 5-19.

In operation, the radio 61 receives outbound data 88 from the hostdevice via the host interface 62. The host interface 62 routes theoutbound data 88 to the baseband processing module 64, which processesthe outbound data 88 in accordance with a particular wirelesscommunication standard (e.g., IEEE 802.11 Bluetooth, et cetera) toproduce outbound time domain baseband (BB) signals.

The digital-to-analog converter 77 converts the outbound time domainbaseband signals from the digital domain to the analog domain. Thefiltering module 79 filters the analog signals prior to providing themto the IF up-conversion module 81. The IF up conversion module 81converts the analog baseband or low IF signals into RF signals based ona transmitter local oscillation 83 provided by local oscillation module100. The power amplifier 83 amplifies the RF signals to produce outboundRF signals 92, which are filtered by the transmitter filter module 85.The antenna 86 transmits the outbound RF signals 92 to a targeted devicesuch as a base station, an access point and/or another wirelesscommunication device.

The radio 61 also receives inbound RF signals 94 via the antenna 86,which were transmitted by a base station, an access point, or anotherwireless communication device. The antenna 86 provides the inbound RFsignals 94 to the receiver filter module 101 via the Tx/Rx switch 73.The Rx filter 71 bandpass filters the inbound RF signals 94 and providesthe filtered RF signals to the low noise amplifier 103, which amplifiesthe RF signals 94 to produce amplified inbound RF signals. The low noiseamplifier 72 provides the amplified inbound RF signals to the IF downconversion module 107, which directly converts the amplified inbound RFsignals into inbound low IF signals or baseband signals based on areceiver local oscillation 81 provided by local oscillation module 100.The down conversion module 70 provides the inbound low IF signal orbaseband signal to the filtering/gain module 68. The filtering module109 filters the inbound low IF signals or the inbound baseband signalsto produce filtered inbound signals.

The analog-to-digital converter 111 converts the filtered inboundsignals into inbound time domain baseband signals. The basebandprocessing module 64 decodes, descrambles, demaps, and/or demodulatesthe inbound time domain baseband signals to recapture inbound data 98 inaccordance with the particular wireless communication standard beingimplemented by radio 61. The host interface 62 provides the recapturedinbound data 92 to the host device 18-32 via the radio interface 54.

As one of average skill in the art will appreciate, the wirelesscommunication device of FIG. 3 may be implemented using one or moreintegrated circuits. For example, the host device may be implemented onone integrated circuit, the baseband processing module 64 and memory 66may be implemented on a second integrated circuit, and the remainingcomponents of the radio 61, less the antenna 86, may be implemented on athird integrated circuit. As an alternate example, the radio 61 may beimplemented on a single integrated circuit. As yet another example, theprocessing module 50 of the host device and the baseband processingmodule 64 may be a common processing device implemented on a singleintegrated circuit. Further, the memory 52 and memory 66 may beimplemented on a single integrated circuit and/or on the same integratedcircuit as the common processing modules of processing module 50 and thebaseband processing module 64.

In the communication system of FIG. 1, the communication device may benewer devices as described with references to FIGS. 2 and 3 or may belegacy devices (e.g., compliant with an earlier version or predecessorof IEEE 802.11n standard). For the newer devices, they may configure thechannel bandwidth in numerous ways as illustrated in FIGS. 4 and 5.

FIG. 4 is a diagram of a configurable spectral mask 130 that includes achannel pass region 112, a transition region 114, and a floor region116. The transition region 114 includes a first attenuation region 118,a second attenuation region 120, and a third attenuation region 122.Such a spectral mask 130 promotes interoperability, coexistence, andsystem capacity by limiting interference to adjacent and other channelsfor a wide variety of applications and/or standards. The out of bandmask (e.g., the transition region 114 and the floor region 116) places alower bound on interference levels that can be expected in receiversregardless of their particular implementation. In an effort to minimizethe interference energy that appears on top of the desired signal, theout of band regions are made as small as possible.

To facilitate the above objective, the channel pass region 112, whichencompasses the desired signal, is of a value as close to the channelbandwidth as feasible. The transition region 114, which bounds theadjacent channel interference and is limited by the bandwidth of thebaseband processing module 64 of FIG. 3 and the intermediate frequencymixing stage of the up-conversion module 81, is selected to minimizesuch interference (i.e., post IF inter-modulation distortion (IMD)). Thefloor region 116, which bounds other channel interference, which isoutside the range of the filters and IMD limits and is generally limitedby the local oscillation 100 phase noise, is selected based onachievable phase noise levels.

For instance, the transition region 114 should have a roll off based onthe shoulder height of IMD, which may be assumed to be produced by a3^(rd) order compressive non-linearity. Based on this assumption, thedistorted transmit signal y(t) as a function of the ideal transmitsignal x(t) can be expressed as: y(t)=x(t)−f(Ax³(t)), where f( ) is abandpass filter that removes any DC or harmonic signals produced by thenon-linearity and A=4/3(1/OIP₃)², where OIP represents “Output 3^(rd)order intercept point”, and in the frequency domainY(f)=X(f)−AX(F)*X(f)*X(f). As such, the distorted signal bandwidth willbe no greater than three times the ideal signal bandwidth.

The floor region 116, which is limited by the local oscillator phasenoise, may be based on L(f) convolved with the power spectral density ofthe ideal transmit signal, where L(f) is defined in IEEE std. 1139-1999as the normalized phase noise spectral density and where y(t)=x(t) l(t)and Y(f)=X(f)*L(f), where x(t) represents the ideal RF signal, l(t) is amodel of the phase nose generated in the local oscillator, y(t)represents the resulting signal, and Y(f) is the resulting signal in thefrequency domain. Note that at 10 MHz or more from the carrier, phasenoise spectrum is relatively flat. From this, a −123 dBc/Hz noise floormay be achieved for 20 MHz channels and a −126 dBc/Hz noise floor may beachieved for 40 MHz channels.

FIG. 5 is a table illustrating a few examples of values for aconfigurable spectral mask 100. While the table includes channel widthsof 10, 20, and 40 MHz, one of average skill in the art will appreciate;other channel widths may be used. Further, the transition region mayinclude more or less attenuation regions than the three shown in FIG. 4.

FIG. 6 is a diagram of a wide bandwidth channel 130 (e.g., 40 MHz) withreference to two legacy channels 132, 134 (e.g., 20 MHz channel N and 20MHz channel N+1) and a legacy guard interval 136. To construct a widebandwidth signal 130 without regard as to whether legacy devices arepresent, the overlapping legacy portions of the two channels 132, 134are considered when establishing the format for the wide bandwidthchannel 130. In one embodiment, the preamble of the wide bandwidthsignal 130 includes a legacy header portion (e.g., a preamble inaccordance with an earlier version or predecessor of IEEE 802.11n)within the header spectral portion of the first channel 132 (e.g.,Channel N) and/or in the second channel 134 (e.g., Channel N+1). Assuch, legacy devices will be able to recognize the frame and, based onthe information contained within the preamble, refrain from transmissionuntil the wide bandwidth signal 130 has been transmitted.

For newer communication devices (i.e., those capable of transceiving thewide bandwidth signals 130), they transmit data and/or headerinformation within the guard band section 136 of legacy channels and inthe channels 132, 134. This expands the amount of data that may betransmitted within frame.

In one embodiment, the preamble and packet header of the wide-bandwidthsignal 130 uses the same spectrum that the payload of the wide-bandwidthsignal 130 will use to provide a legitimate preamble and packet headersthat can be transmitted in the portion of the spectrum used by legacydevices. Further, energy of the signal is transmitted in the legacyguard bands 136 so that the receiver may perform reliable preambleprocessing (carrier detection, gain control, channel estimation, etc.)on the wide-bandwidth signal 130.

In an embodiment, the multiple-channel legacy preambles and packetheaders will allow legacy-station reception of the preamble and reliablecarrier detection, gain control, and channel estimation over the legacychannels. The guard-band transmission allows for reliable carrierdetection, gain control, and channel estimation for the remainder of thespectrum (which will be used for transmission of the wide-bandwidthpayload). Further, legacy stations are generally tolerant of adjacentchannel transmissions which are at the same power as the desired signal.Still further, legacy stations will see legitimate preambles and packetheaders so that they will be able to detect that a signal is present,perform gain control, channel estimation, and other preamble processing,and/or decode the packet header and thereby defer transmission until theend of the wide-band transmission. Yet further, the energy transmittedin the guard band will be disregarded by the receiver and will thereforenot hinder the reception of the legacy components of the wide-bandsignal.

For the newer devices (e.g., IEEE 802.11n compliant), the devices willhave more energy for carrier detection, be able to perform a betterestimate of received power, thereby being able to do better gain controlon the packet, be able to estimate the channel response in the guardband (for use during payload demodulation), and have full access to themedium since legacy stations can see the transmission and defer untilits end.

FIG. 7 is a diagram depicting a wireless communication between twowireless communication devices 100 and 102 that are in a proximal regionwhere the only protocol that is used is IEEE 802.11n. The wirelesscommunication may be direct (i.e., from wireless communication device towireless communication device), or indirect (i.e., from a wirelesscommunication device to an access point to a wireless communicationdevice). In this example, wireless communication device 100 is providingframe 104 to wireless communication device 102. The frame 104 includes awireless communication set-up information field 106 and a data portion108. The wireless communication set-up information portion 106 includesa short training sequence 157 that may be 8 microseconds long, a 1^(st)supplemental long training sequence 159 that may be 4 microseconds long,which is one of a plurality of supplemental long training sequences 161,and a signal field 163 that may be 4 microseconds long. Note that thenumber of supplemental long training sequences 159, 161 will correspondto the number of transmit antennas being utilized for multiple inputmultiple output radio communications.

The data portion of the frame 104 includes a plurality of data symbols165, 167, 169 each being 4 microseconds in duration. The last datasymbol 169 also includes a tail bits and padding bits as needed.

FIG. 8 is a diagram of a wireless communication between two wirelesscommunication devices 100 and 102, each of which is compliant with IEEE802.11n. Such a communication is taking place within a proximal areathat includes 802.11n compliant devices, 802.11a compliant devicesand/or 802.11g compliant devices. In this instance, the wirelesscommunication may be direct or indirect where a frame 110 includes alegacy portion of the set-up information 112, remaining set-upinformation portion 114, and the data portion 108.

The legacy portion of the set-up information 112 includes a shorttraining sequence 157, which is 8 microseconds in duration, a longtraining sequence 171, which is 8 microseconds in duration, and a signalfield 173, which is 4 microseconds in duration. The signal field 173, asis known, includes several bits to indicate the duration of the frame110. As such, the IEEE 802.11a compliant devices within the proximalarea and the 802.11g compliant devices within the proximal area willrecognize that a frame is being transmitted even though such deviceswill not be able to interpret the remaining portion of the frame. Inthis instance, the legacy devices (IEEE 802.11a and IEEE 802.11g) willavoid a collision with the IEEE 802.11n communication based on a properinterpretation of the legacy portion of the set-up information 112.

The remaining set-up information 114 includes additional supplementallong $S_{k} = {\begin{bmatrix}s_{10,k} & s_{11,k} & s_{12,k} \\s_{20,k} & s_{21,k} & s_{22,k} \\s_{30,k} & s_{31,k} & s_{32,k}\end{bmatrix} = \begin{bmatrix}s_{00,k} & {s_{00,k} \cdot {\mathbb{e}}^{{\mathbb{i}} \cdot \theta_{k}}} & {s_{00,k} \cdot {\mathbb{e}}^{{\mathbb{i}} \cdot \phi_{k}}} \\s_{00,k} & {s_{00,k} \cdot {\mathbb{e}}^{{\mathbb{i}} \cdot {({\theta_{k} - \frac{4 \cdot \pi}{3}})}}} & {s_{00,k} \cdot {\mathbb{e}}^{{\mathbb{i}} \cdot {({\phi_{k} - \frac{2 \cdot \pi}{3}})}}} \\s_{00,k} & {s_{00,k} \cdot {\mathbb{e}}^{{\mathbb{i}} \cdot {({\theta_{k} - \frac{2 \cdot \pi}{3}})}}} & {s_{00,k} \cdot {\mathbb{e}}^{{\mathbb{i}} \cdot {({\phi_{k} - \frac{4 \cdot \pi}{3}})}}}\end{bmatrix}}$ θ_(k) = π ⋅ k/(4 ⋅ N_(subcarriers))ϕ_(k) = π ⋅ (k + 4)/(2 ⋅ N_(subcarriers))training sequences 159, 161, which are each 4 microseconds in duration.The remaining set-up information further includes a high data signalfield 163, which is 4 microseconds in duration to provide additionalinformation regarding the frame. The data portion 108 includes the datasymbols 165, 167, 169, which are 4 microseconds in duration aspreviously described with reference to FIG. 7. In this instance, thelegacy protection is provided at the physical layer.

FIG. 9 is a diagram of a wireless communication between two wirelesscommunication devices 100 and 102 that are both IEEE 802.11n compliant.The wireless communication may be direct or indirect within a proximalarea that includes IEEE 802.11 compliant devices, IEEE 802.11a, 802.11band/or 802.11g devices. In this instance, the frame 111 includes alegacy portion of the set-up information 112, remaining set-upinformation 114 and the data portion 108. As shown, the legacy portionof the set-up information 112, or legacy frame, includes an IEEE 802.11PHY preamble (i.e., STS 157, LTS 171, and signal field 173) and a MACpartitioning frame portion 175, which indicates the particulars of thisparticular frame that may be interpreted by legacy devices. In thisinstance, the legacy protection is provided at the MAC layer.

The remaining set-up information 114 includes a plurality ofsupplemental long training sequences 159 161 and the high data signalfield 163. The data portion 108 includes a plurality of data symbols165, 167, 169 as previously described.

FIG. 10 is a diagram of a backward compatible signaling format. Thesignaling format includes a legacy preamble 140, a signal field 142, anextended preamble 144, a plurality of additional signal fields 146, 150,154, a plurality of data units (Service/PSDU) 148, 152, 156, and aninterframe gap 158. In general, the frame format is as previouslydescribed with reference to FIGS. 8 and 9, where the initial signalfield 142 is used to inform the legacy devices of the duration of theframe so that the legacy devices do not attempt to access the channelwhile it is in use by newer devices. The signal field 142 is furtherused to inform the newer devices (e.g., the IEEE 802.11n compliantdevices) of the channel usage for 802.11n transmission and the number oftransmit antennas for the transmission.

The additional signal fields 146, 150, 154 indicate the rate/mode, thelength (in bytes) of the frame, the last PSDU in the frame (or burst),whether a PSDU immediate ACK is required, and error checkingcapabilities. The rate/mode portion may be six bits in length to:implicitly convey number of transmit antennas, (legacy signal field willbe absent in homogeneous 802.11n case); implicitly convey channel width(802.11n signal field transmitted by either 20 MHz or 40 MHz channeldevices should be receivable by either 20 MHz or 40 MHz channeldevices); assume PHY data rates spanning 6 mbps through 448 mbps, withroughly 33% throughput increase with each higher data rate, 16 rates arerequired, or 4 bits; and/or allow 4 modes for achieving any given rate(varying channel width, subcarrier constellation size, number oftransmit antennas, etc.), or 2 bits.

The length portion of the signal field(s) may be 12 bits to: allow PSDUsup to 4095 bytes long as in legacy case; MAC level extension for PSDUbursting need not be represented in Length (e.g.: as a Burst ID or BurstLength) since Burst length may actually be unknown at start of burst or,even if burst length is known, need only be conveyed once at start orend of burst, no need to index PSDUs in a Burst at PHY level, (MACmethods exist for unique PSDU identification).

The last PSDU portion of the signal field(s) 146, 150, 154 may be 1 bitto, as explained above, convey burst length once at end of burst, with abit denoting “Last PSDU”. The immediate ACK portion of the signalfield(s) may be 1 bit to resolve contention between responding deviceswhen a series of immediate MAC acknowledgements are required to theseries of PSDUs in a transmitted burst.

In another embodiment, 26-30 bits may be used per signal field(s) 146,150, 154 to convey the rate/mode (6 bits), length (12 bits), last PSDU(1 bit), immediate ACK (1 bit), CRC (4 bits), with 2-6 bits reserved.The CRC section offers error detection.

Further, legacy coding and modulation use rate ½ convolutional code andBPSK in 48 data bearing subcarriers, which allow 24 uncoded bits persignal field, of which 18 information bits are available, the remaining6 bits providing tail bits for immediate decoding. For .11ncommunications, the signal field uses 26-30 information bits per signalfield, yet remain at least as robust in performance (comparableSignal-to-Noise Ratio required to achieve a given Probability of SignalField Error), and offer superior error detection capability.

Modulation for the frame may include QPSK in 48 data bearingsubcarriers, allowing 96 coded bits per signal field 146, 150, 154 and,for 40 MHz channels, may include replicate 48 subcarrier usage in upperand lower 20 MHz halves to allow .11n signal field demodulation by 20MHz channel .11n devices.

The coding may include several options. The first option assumes 6Reserved info bits and employs legacy constraint length 6, rate ½convolutional code, G=[133, 171], inserting 18 “tail” bits, (12 inaddition to 6 legacy tail bits) to allow perfect knowledge of encoderstate at 3 points in transmitted sequence. Further, uncoded bits and“tail” are arranged as follows:[10 info, 6 tail, 10 info, 6 tail, 10 info, 6 tail]=30 info bits +18tail bits=48 uncoded bits, or 96 coded bits per signal field.

The second option 2 assumes 4 Reserved info bits and employs an outer(6,4) RS block code over GF(27), followed by an inner legacy constraintlength 6, rate ½, convolutional code, G=[133, 171], appending 6 tailbits. The 28 info bits are grouped into 4 GF(27) elements, 14 paritybits or 2 GF(27) elements are added by RS encoding, resulting in 42block coded bits or 1 RS block; tail bit addition results in 48un-convolutionally-coded bits, or 96 concatenated coded bits per signalfield.

The third option assumes 2 Reserved info bits and employs a constraintlength 6, rate ⅓ convolutional code, G=[117, 127, 155], appending 6 tailbits. The 26 info bits+6 tail bits=32 uncoded bits, or 96 coded bits persignal field.

FIG. 11 is a diagram of the frame where only newer devices (e.g.,802.11n compliant devices) are present in a proximal area of thewireless local area network. In this instance, the signaling formatincludes a native preamble 160, a plurality of additional signal fields162, 166, 170, a plurality of data units (Service/PSDU) 164, 168, 172,and an interframe gap 174. The signal fields 162, 166, 170 convey thesame information as the signal fields 142, 146, 150, 154 with referenceto FIG. 10.

As one of average skill in the art will appreciate, the term“substantially” or “approximately”, as may be used herein, provides anindustry-accepted tolerance to its corresponding term. Such anindustry-accepted tolerance ranges from less than one percent to twentypercent and corresponds to, but is not limited to, component values,integrated circuit process variations, temperature variations, rise andfall times, and/or thermal noise. As one of average skill in the artwill further appreciate, the term “operably coupled”, as may be usedherein, includes direct coupling and indirect coupling via anothercomponent, element, circuit, or module where, for indirect coupling, theintervening component, element, circuit, or module does not modify theinformation of a signal but may adjust its current level, voltage level,and/or power level. As one of average skill in the art will alsoappreciate, inferred coupling (i.e., where one element is coupled toanother element by inference) includes direct and indirect couplingbetween two elements in the same manner as “operably coupled”. As one ofaverage skill in the art will further appreciate, the term “comparesfavorably”, as may be used herein, indicates that a comparison betweentwo or more elements, items, signals, etc., provides a desiredrelationship. For example, when the desired relationship is that signalI has a greater magnitude than signal 2, a favorable comparison may beachieved when the magnitude of signal 1 is greater than that of signal 2or when the magnitude of signal 2 is less than that of signal 1.

The preceding discussion has presented various embodiments for wirelesscommunications in a network that includes legacy devices. As one ofaverage skill in the art will appreciate, other embodiments may bederived from the teachings of the present invention without deviatingfrom the scope of the claims.

1. A method for wireless communication, the method comprises:determining whether legacy devices are within a proximal region of thewireless communication; when at least one legacy device is within theproximal region, formatting a frame to include at least one of: a legacypreamble; a signal field; an extended preamble; at least one additionalsignal field; at least one service field; an inter frame gap; and a datafield.
 2. The method of claim 1 further comprises: when at least onelegacy device is not within the proximal region, formatting a frame toinclude: a native preamble; at least one signal field; at least oneservice field; an inter frame gap; and a data field.
 3. The method ofclaim 2, wherein the at least one signal field comprises at least oneof: rate/mode information; length information; last data unit in theframe indication; data unit acknowledgment requirement; and errorchecking capability.
 4. The method of claim 3, wherein the rate/modeinformation comprises at least one of: implicit number of transmitantennas; implicit channel width; and physical layer data rate.
 5. Themethod of claim 3, wherein the length information comprises at least oneof: bytes of PSDU [PLCP (physical layer convergence procedure) ServiceData Unit].
 6. The method of claim 2 further comprises at least one of:coding the at least one signal field using a rate ½ convolutional code;coding the at least one signal field using an outer Reed-Solomon blockcode and an inner coding of the rate ½ convolutional code; and codingthe at least one signal field using a rate ⅓ convolutional code with aconstraint length of six.
 7. The method of claim 2 further comprises atleast one of: for a legacy channel, utilizing a quadrature phase shiftkeying (QPSK) for the at least one signal field; and for a widebandwidth channel: utilizing QPSK for subcarriers of a first portion ofthe wide bandwidth channel, wherein the first portion has a bandwidthcorresponding to the legacy channel; and replicating the first portionfor a second portion of the wide bandwidth channel.
 8. The method ofclaim 1, wherein the signal field comprises at least one of: rate/modeinformation; length information; last data unit in the frame indication;and number of antennas.
 9. A radio frequency (RF) transmitter comprises:a baseband processing module operably coupled to convert outbound datainto an outbound symbol stream; and a transmitter section operablycoupled to convert the outbound symbol stream into outbound RF signals,wherein the baseband processing module is operably coupled to: determinewhether legacy devices are within a proximal region of the wirelesscommunication; when at least one legacy device is within the proximalregion, format a frame to include at least one of: a legacy preamble; asignal field; an extended preamble; at least one additional signalfield; at least one service field; an inter frame gap; and a data field.10. The RF transmitter of claim 9, wherein the baseband processingmodule is further operably coupled to: when at least one legacy deviceis not within the proximal region, format a frame to include: a nativepreamble; at least one signal field; at least one service field; aninter frame gap; and a data field.
 11. The RF transmitter of claim 10,wherein the at least one signal field comprises at least one of:rate/mode information; length information; last data unit in the frameindication; data unit acknowledgment requirement; and error checkingcapability.
 12. The RF transmitter of claim 11, wherein the rate/modeinformation comprises at least one of: implicit number of transmitantennas; implicit channel width; and physical layer data rate.
 13. TheRF transmitter of claim 11, wherein the length information comprises atleast one of: bytes of PSDU [PLCP (physical layer convergence procedure)Service Data Unit].
 14. The RF transmitter of claim 10, wherein thebaseband processing module is further operably coupled to, at least oneof: code the at least one signal field using a rate ½ convolutionalcode; code the at least one signal field using an outer Reed-Solomonblock code and an inner coding of the rate ½ convolutional code; andcode the at least one signal field using a rate ⅓ convolutional codewith a constraint length of six.
 15. The RF transmitter of claim 10,wherein the baseband processing module is further operably coupled to,at least one of: for a legacy channel, utilize a quadrature phase shiftkeying (QPSK) for the at least one signal field; and for a widebandwidth channel: utilize QPSK for subcarriers of a first portion ofthe wide bandwidth channel, wherein the first portion has a bandwidthcorresponding to the legacy channel; and replicate the first portion fora second portion of the wide bandwidth channel.
 16. The RF transmitterof claim 9, wherein the signal field comprises at least one of:rate/mode information; length information; last data unit in the frameindication; and number of antennas.